19 June 2010

Conquest of the land, a la Chubby Checker

Now this is wild:

It’s a fish. It jumps.

This picture was not taken in an aquarium filled with water; it’s in air.

The fish is a blenny, Alticus arnoldorum, and a new paper introduced me to this fish that barely deserves to be called a fish. According to the author, Shi-Tong Hsieh, this fish spends so much time on land that it actively defends territory on land. It can stay out of water indefinitely, as long as it stays moist.

That blows my mind.

Hsieh was interested how blennies were able to be so agile on land, so she recorded high speed video of several species and did detailed analysis of the movement. The leaping blenny above is the most active on land.

The big finding is that these terrestrial blennies are able to rotate their tail. That it, they can move it clockwise or counterclockwise relative to the axis of their bodies, not simply move it back and forth. When these fish jump, they are pushing off with the side of their tails, not the bottom.

The terrestrial blennies are able to jump about twice as far as their aquatic relatives, which can’t twist the tail. Although there isn’t enough evidence to say that this ability to rotate the tail caused the performance increase, it certainly is mighty suspicious.

Hsieh suggests that this jumping behaviour may be related to C-starts, which are fish escape responses I’ve mentioned before here and here. This would be tricky to test: the neurons are huge, but active behaviours like jumping make it difficult to record the activity.

An easier follow-up would probably be to start looking closely at the musculature and innervation of these terrestrial blennies to figure out exactly what has changed in the skeleton and / or muscles that allow them to do the twist.